This study was a clinical trial to determine the safety and efficacy of cysteamine in the treatment of nephropathic cystinosis, a rare inborn metabolic disease which usually leads to end-stage renal disease before 10 years of age. All children enrolled in the trial received oral cysteamine. Control information was provided by data collected on 64 patients who participated in a previous trial evaluating ascorbic acid for the treatment of this disease. The cysteamine trial enrolled 94 patients; analysis of data is completed, and major findings have been published.